Safety and the prevention of falls is of primary importance for individuals working at heights, around areas of excavation, or where a fall could result in serious injury or death. In such cases the employment of a safety system to prevent falls is often not only desirable but a statutory requirement. Typically, safety systems that are commonly used involve the placement of a harness or belt around an individual and then the subsequent use of a rope, cable or strap that physically secures the individual, by way of the belt, to a solid structure. For example, individuals working on bridges, towers or tall buildings will commonly wear belts, safety harnesses or fall arresters that include a lifeline most typically comprised of a rope or strap having one end secured to a structural feature of the device upon which the individual is working. In the logging industry and in situations where individuals work on utility poles, a worker is often fitted with a safety belt having a rope or strap that is connected to the belt at one end, is passed around the tree or pole, and then has its free end connected to the opposite side of the belt. So that the worker may readily engage and disengage the lifeline, rope, cable or strap, at least one end must be fitted with a means to releasably secure it to a solid or safe structure. The other end of the rope or strap may be equally fitted with a means to releasably secure it to the worker's belt or harness, or it may be a more permanent attachment.
In theory, should a worker slip or fall while wearing a safety belt or a harness that is securely attached by way of a lifeline to a solid structure, the worker will only be allowed to fall a very few feet after which his decent will be stopped and he will be suspended until he can regain his balance or be rescued. Unfortunately in practice the safety harness and fall arrest systems currently in use do not always function as designed and accidents, injuries and fatalities sometimes occur. One type of failure that can have disastrous results is a consequence of the use of snap hooks on the end of a lifeline.
Due to their convenience and ease of use, snap hooks having a gate keeper that encloses the hook bowl, are probably the most widely used method to secure the end of a lifeline. Since standard snap hooks can become unintentionally opened through the application of a force against the gate keeper, others have proposed and developed a variety of different locking mechanisms that assist in maintaining the gate keeper in a closed position. While such locking mechanisms have reduced the likelihood of an unintentional opening of the hook, they too suffer from their own limitations. For example, one of the most common locking snap hooks currently in use requires an individual to grasp in his hand both the gate keeper and a locking lever and squeeze them inwardly toward each other in order to "open" the hook. Moving the locking lever inwardly effectively "unlocks" the gate keeper allowing it to also move inwardly so that the hook may be placed over an object or removed therefrom. One of the reasons for the success of this form of locking snap hook is its relative ease of use since an individual can effectively operate the hook through grasping it in one hand. However, the ease of operation of such snap hooks can also result in their unintentional disengagement. Disengagement can occur where the hook is accidentally compressed such that both the locking lever and the gate keeper are pushed inwardly toward the hook bowl at the same time. It has been found that situations as innocuous as leaning against a hook that is bearing against a solid surface can be sufficient to cause accidental disengagement.